The present invention relates to a linear motor.
A linear motor which includes a stator and a movable element linearly reciprocating along the stator comprises a plurality of permanent magnets arranged in one or two rows and an armature. Japanese Patent Publication No. 11-206100 discloses a linear motor which includes a stator provided with a magnetic pole row, and a movable element provided with an armature. The armature includes an armature core constituted by stacking a plurality of magnetic steel sheets, and a plurality of winding portions. The armature core includes a yoke extended in a moving direction of the movable element, and a plurality of magnetic pole portions which are extended toward the magnetic pole rows from the yoke and are wound with a winding conductor. Japanese Patent Publication No. 2002-176762 discloses a linear motor of a kind as shown in Japanese Patent Publication No. 11-206100, in which magnetic pole surface constituent portions, which are opposed to the magnetic pole row, of two adjacent magnetic pole portions are connected to each other. Japanese Patent Publication No. 2003-158864 discloses a linear motor of a kind as shown in Japanese Patent Publication No. 11-206100, in which a plurality of magnetic pole portions each include a plurality of first magnetic pole portions which are respectively provided with a wound portion wound with a winding conductor, and a plurality of second magnetic pole portions which are not wound with a winding conductor. The first magnetic pole portions and the second magnetic pole portions are extended in an opposing direction in which the stator and the movable element are opposed to each other, and are alternately arranged at a predetermined interval in a moving direction of the movable element so that the second magnetic pole portion is located on each end of the magnetic pole portion in the moving direction of the movable element.
However in the conventional linear motors described above, when dimensions of the linear motors are reduced in an orthogonal direction orthogonal to the moving direction and the opposing direction as previously described, a thickness of the magnetic pole portion is accordingly reduced, thereby reducing the magnetic fluxes which flow between the magnetic pole portion and the magnetic pole row. Consequently, a thrust force is reduced. Japanese Patent Publication No. 2001-8432 discloses a linear motor which comprises a magnetic pole portion including a wound portion which is wound with a winding conductor and a non-wound portion which is not wound with a winding conductor and is integrally provided at ends of the wound portion. A dimension of the non-wound portion in the orthogonal direction is defined larger than that of the wound portion in the orthogonal direction. With this arrangement, then magnetic fluxes which flow between the magnetic pole portion and the magnetic pole row is not reduced. Accordingly it is possible to suppress a reduction of the thrust force.
In the linear motor of Japanese Patent Publication No. 2001-8432, through holes through which screws or the like pass are formed in the armature core. The armature core is secured onto a movable stage which can be moved along the stator, with the screws passing through the through holes. In the linear motor of Japanese Patent Publication No. 2001-8432, the armature core is constituted by stacking a plurality of magnetic steel sheets formed in a predetermined shape, in the moving direction of the movable element. Therefore, in the linear motor of Japanese Patent Publication No. 2001-8432, the through holes are formed after stacking the plurality of magnetic steel palates, by cutting or other means in a direction orthogonal to the direction in which the magnetic steel sheets have been stacked. Thus, manufacturing the armature core is troublesome. In the linear motor of Japanese Patent Publication No. 2001-8432, a dimensional error is likely to be caused in an interval (slot pitch) between two adjacent magnetic pole portions of the armature core.